The present invention relates generally to water heaters, and more particularly relates to the supply of combustion air to floor mountable, fuel-fired water heaters.
Floor mounted, fuel-fired domestic water heaters are typically of a cylindrical configuration with floor support legs depending from the bottom end of the heater. With the water heater in its normal operating position, the support legs engage the floor and support the water heater in a vertical position with the bottom end of the cylindrical heater structure spaced a few inches above the floor.
The elevated bottom end of the water heater typically has a suitable combustion air inlet formed therein directly beneath a fuel burner disposed within the interior of the water heater. Fuel (such as natural gas) is supplied to the burner via a fuel line in which a fuel valve is interposed, the fuel valve being mounted on an exterior side surface portion of the water heater. During operation of the water heater, fuel supplied to the burner is mixed with combustion air drawn upwardly through the heater's bottom end opening to form a fuel-air mixture which is burned and used to heat water held in an internal storage tank portion of the heater for periodic supply to a variety of hot-water using devices.
When the water heater is to be installed in an area in which flammable liquids (such as gasoline) are to be stored the water heater may be supported in an elevated relationship with the floor--by, for example, mounting the heater on a suitable pedestal structure--to maintain a minimum floor-to-burner vertical clearance distance of at least 18". Leg extension kits, and other heater elevating apparatus, may also be used to achieve this result.
The goal in maintaining this minimum floor-to-burner vertical clearance is to position the burner generally above the level of heavier-than-air flammable vapors which may have settled to the floor adjacent the water heater, to thereby materially lessen the possibility that the operating burner, or related pilot or ignition components of the heater, will ignite the fumes. The purpose in positioning the burner above an anticipated flammable vapor level can occasionally be defeated, however, by the combustion updraft created by burner operation. This updraft, which beneficially serves to draw combustion air upwardly to the burner through the bottom air inlet in the heater body, is sometimes strong enough to also draw adjacent flammable vapors upwardly into contact with the burner flame, the pilot flame, or related hot ignition apparatus. In such instances, of course, the positioning of the burner a substantial distance above the floor, even though in strict compliance with applicable safety codes is to no avail. This elevation thereof the water heater above the floor can also create vertical clearance problems when the water heater is to be installed in areas having low ceilings.
It can be readily be seen from the foregoing that it would be desirable to provide improved apparatus and methods for isolating the burner in a floor mounted, fuel fired water heater from flammable vapors adjacent the floor near the heater. It is accordingly an object of the present invention to provide such improved apparatus and methods.